Re: multithreading in Batch/pipelining mode for libpq

On 2017-04-22 09:14:50 +0800, Craig Ringer wrote:
> 2) if the answer to the previous question is negative, is it possible to
> send asynchronous queries in one thread while reading results in another
> thread?
>
>
> Not right now. libpq's state tracking wouldn't cope.
>
> I imagine it could be modified to work with some significant refactoring.
> You'd need to track state with a shared fifo of some kind where dispatch
> outs queries on the fifo as it sends them and receive pops them from it.

FWIW, I think it'd be a *SERIOUSLY* bad idea trying to make individual
PGconn interactions threadsafe. It'd imply significant overhead in a lot
of situations, and programming it would have to become a lot more
complicated (since you need to synchronize command submission between
threads). For almost all cases it's better to either use multiple
connections or use a coarse grained mutex around all of libpq.

- Andres